In a distributed file system such as a network file system (NFS), when a file is accessed from many client machines concurrently, a high load may be applied to a server machine and the rate of the access to the file may be significantly reduced. This is mainly due to the fact that a disk wait period increases due to a conflict in access to a disk device connected to the server machine.
As a technique for controlling access to a file, the following technique is known. A percentage to be used is assigned to each of users, and factors of all applications to be executed by the users are determined. The factors are associated with requests to search data from an arbitrary application. Times to start the requests to search the data are calculated for batches of the data requests in accordance with the associated factors. As a result, the times to start the requests by all users corresponding to the batches are aligned based on the calculated start times. A system readjusts the start times in order for the system to efficiently operate (for example, a technique described in Japanese Laid-Open Patent Publication No. 2000-172541).
A multiplicity is set for each data managing device. A data managing device with a high multiplicity processes a large number of search requests concurrently and processes each search request for a long time, while a data managing device with a low multiplicity processes a smaller number of search requests concurrently and processes each search request for a short time. A service server estimates a processing time for each of search requests from a user terminal, assigns a search request to be processed for a long time to the data managing device with the high multiplicity, assigns a search request to be processed for a short time to the data managing device with the low multiplicity, and thereby improves the efficiency of a search request process. The search request to be processed for the short time is processed and completed by the data managing device with the high multiplicity for the short time. Even if the number of search requests to be concurrently processed is too large, a time for processing the search requests is not too long, compared with the case where the search requests are not concurrently processed, and the number of search requests to be concurrently processed in an overall system increases (for example, a technique described in Japanese Laid-Open Patent Publication No. 2010-152435).
In addition, as techniques for controlling access to a file, there are techniques described in Japanese Laid-Open Patent Publications Nos. 2002-358259, 2006-067401, and 2007-188452, for example.
In the distributed file system, a time for each access may be longer by multiple times than a time for independently executed access. Thus, fairness between users may not be secured, especially when a high load is applied.